**Classify angles**

• *Acute, obtuse, right, and straight angles*

o Acute angles measure less than 90 degrees

o Obtuse angles measure more than 90 degrees

o Right angles measure exactly 90 degrees

o Straight angles measure exactly 180 degrees

• *Complementary angles*

o Complementary angles are angles whose sum equal 90 degrees

• *Supplementary angles*

o Supplementary angles are angles whose sum equal 180 degrees

• *Vertical angles*

o Vertical angles are formed by intersecting two lines, and the opposite angles are equal

**Classify triangles**

• *Classify by sides*

o Equilateral triangles have **all equal sides **of measurement

o Isosceles triangles have **two equal sides** of measurement

o Scalene triangles have **different sides **of measurement

• *Classify by angles*

o Acute triangles are triangles with **all acute **angles

o Obtuse triangles are triangles with **one obtuse **angle

o Right triangles are triangles with **one right **angle

• *Sum of all angles = 180 degrees*

• *Perimeter of triangles*

o The perimeter is the distance around the shape.

o To determine the perimeter of a triangle, add the measurements of all three sides.

• *Area of triangles*

o To determine the area of a triangle, multiply the base times the height, and then divide that product by two. The formula is: A = (b x h)/2

o Area units are always squared.

**Classify polygons**

• *Classify by number of sides*

3-sides – triangles

4-sides – quadrilaterals

5-sides – pentagons

6-sides – hexagons

8-sides – octagons

10-sides – decagons

12-sides – dodecagons

**Circles**

• *Radius, diameter*

o The radius is the measurement from the center of the circle to any point on the circle.

o The diameter is the measurement from two points on the circle, where the line passes through the center.

• *Circumference of circle*

o The circumference of a circle is the distance around the circle.

o To determine the circumference, multiply the diameter of the circle times pi (approximate value of 3.14).

• *Area of circle*

o The area of a circle is the measurement of the space inside the circle.

o To determine the area, square the radius, and multiply by pi (approximate value of 3.14).

o Area units are always squared.

**Pythagorean Theorem**

• *The Pythagorean Theorem* only applies to right triangles

• *The Pythagorean Theorem *is used to determine the distance of one of the sides of a right triangle when the other two distances are known.

• The side opposite of the right angle is known as the hypotenuse, and it is labeled as “c.”

• The other two sides of the right triangle are known as the legs, and they are labeled as “a” and “b” – in no particular order.

• Use the formula a^2 + b^2 = c^2, where ^ means to square.

o Use the property of equality of solve for the missing value.